Multiple power mode amplifier with bias modulation option and without bypass switches

ABSTRACT

A multiple power mode amplifier provides a low and a high power mode without using switches. This amplifier may be used in radio frequency (RF) applications such as mobile telephones, pagers, portable digital assistants, and wireless e-mail devices. In the low power mode, the power consumption of the amplifier is reduced, which will increase operation time, especially important for battery-operated devices. In one implementation, the amplifier includes a number of impedance matching network units ( 130, 140, 150 , and  160 ), impedance transformer ( 170 ), and a power stage ( 120 ). An implementation provides further power consumption savings by modulating a bias of an amplifier stage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. provisional application60/514,420, filed Oct. 23, 2003 and is a continuation-in-part of U.S.patent application Ser. No. 10/435,529, filed May 9, 2003, which claimspriority under 35 U.S.C. § 119 to Korean patent application number2003-308, filed on Jan. 3, 2003, which is incorporated by reference,along with all other references cited in this application.

BACKGROUND OF THE INVENTION

The present invention relates to a power amplifier, especially a radiofrequency (RF) amplifier used in mobile handset and otherbattery-powered applications (e.g., portable wireless devices, personaldigital assistants (PDAs), notebook computers, and others). Moreparticularly, the present invention relates to a multiple power modepower amplifier with high efficiency appropriate for amplifying powercorresponding to various output power levels without using bypassswitching circuits.

Mobile handsets or mobile telephones (also sometimes called cell phones)for wireless communication services are becoming smaller and lighter.This also means a size of the battery, which is a typically a sizeableportion of a mobile handset, is also becoming smaller in order tofacilitate a smaller and lighter mobile handset. But at the same time atelephone and its battery is becoming smaller, it is desirable to extenda talk time of a mobile handset. As can be appreciated, these aredifficult goals to reconcile; if the power drain of a device remains thesame and the battery is smaller, operating time of the device perbattery charge becomes shorter.

In a conventional mobile handset, the radio frequency (RF) poweramplifier consumes most of the power of the overall system of the mobilehandset. Thus, low efficiency of the RF power amplifier degrades theefficiency of the overall system, drains the battery more rapidly, andthus reduces the talk time. For this reason, much research in this fieldconcentrates on increasing the efficiency of the RF power amplifier. Ifthe RF power amplifier is more efficient, this reduces power drain andthe battery, which in turn increases talk time or the operating time ofthe device per batter charge.

A multiple power mode power amplifier is one of the devices introducedrecently as a result of such research conducted to increase efficiencyof the RF power amplifier. The multiple power mode power amplifier isconfigured to operate its own power stage corresponding to a desiredsituation and is operated in one of several operation modescorresponding to output power levels, as discussed in U.S. Pat. Nos.5,152,004; 5,175,871; 5,276,912; 5,530,923; 5,661,434; 5,758,269;5,909,643; 6,060,949; 6,069,526; and 6,356,150, all of which areincorporated by reference. Bypass switching circuits have been used forsuch operations of the multiple power mode power amplifier.

If low output power is required, it is desirable to adjust a path ofpower transmission to bypass a power stage. In contrast, if the highoutput power is required, it is desirable to adjust a path of powertransmission to pass the power stage in order to provide high outputpower. Using a conventional multiple power mode power amplifier (whichuses bypass switches) that selectively performs mode transitioncorresponding to desired output power levels, it is possible to reduceDC power consumption at the time of transferring signals of low outputpower.

However, the multiple power mode power amplifier with switches (e.g.,PIN diodes) is relatively costly to manufacture and the switches reduceefficiency somewhat because they may have negative gain (e.g., −1 dBgain per switch). Further, more than one power stage among a pluralityof power stages connected to each other in serial should be switched inorder to implement the multiple power mode power amplifiers, and morethan one bypass switching circuits and a complex logical control circuitfor controlling the bypass switching circuits are required for theswitching operation.

Power losses caused by switching operations at the bypass switchingcircuits causes a reduction of output power and the reduction of outputpower causes reduction of efficiency of the multiple power mode poweramplifier. Further, there is another problem in that an adjacent channelpower ratio (ACPR) gets worse. Furthermore, the size of the entiresystem gets larger due to bypass switching circuits themselves and thecomplex logical control circuit additionally added for controlling thebypass switching circuits, so that the conventional multiple power modepower amplifier is considered as regressive considering a trend towardsa smaller-sized mobile handset. Also the enlarged size of the entiresystem is disadvantageous in price competitiveness, particularly sincethe switches are expensive components.

Therefore, it is a need to provide a more power efficient poweramplifier, and in particular, a multiple power mode amplifier that doesnot use any switches.

SUMMARY OF THE INVENTION

The present invention is a multiple power mode power amplifier thatamplifies power of various levels with a bypass circuit not includingswitches, so that problems of power loss, increased size, and increasedcost associated with conventional multiple power mode power amplifierusing bypass switches may be avoided. Further, the multiple power modepower amplifier of the invention reduces DC power consumption in the lowpower mode, so that power added efficiency (PAE) characteristics of thepower amplifier is improved and operation time of a portable electronicdevice (e.g., talk time of a mobile handset) equipped with the presentmultiple power mode power amplifier may be extended.

In one embodiment, the multiple power mode amplifier uses a variablegain amplifier as a driver to minimize power loss associated with theconventional multiple power mode power amplifier in the high power mode,so that PAE characteristics in the high power mode may be improved andpoor linearity in the high power mode may be solved. In addition,improvement in sound quality and size reduction of the mobile handsetmay be obtained in a mobile handset or telephone equipped with thepresent multiple power mode power amplifier.

An embodiment of the present invention solves at least the aboveproblems of the conventional multiple power mode power amplifier usingbypass switches and provides a multiple power mode power amplifier withhigh efficiency that may amplify power of various levels without usingbypass switches by making a path for bypassing a power stage and a pathfor passing through a power stage joined at an optimum point andproviding an optimum impedance transformer on the path for bypassing thepower stage.

In an embodiment, the invention is a multiple power mode power amplifierwith high efficiency including a power stage for receiving poweramplified by a driver through a first impedance matching unit connectedin serial to the driver amplifying input power and a second impedancematching unit connected to the first impedance matching unit,reamplifying the power and outputting the reamplified power; an appliedvoltage control circuit, connected to the power stage, for controllingapplied voltages corresponding to a first power mode and a second powermode; an impedance transformer for receiving power amplified by thedriver through the first impedance matching unit, according tooperations of the applied voltage control circuit; a third impedancematching unit, connected to the power stage in serial, for receivingpower amplified by the power stage, according to operations of theapplied voltage control circuit; and a fourth impedance matching unit,connected to the third impedance matching unit and connected to theimpedance transformer, for transferring power, transferred from thethird impedance matching unit or the impedance transformer, to an outputstage according to operations of the applied voltage control circuit.

According to one implementation, the power stage is connected to thesecond impedance matching unit in serial, and in the second power mode,the power stage receives power amplified by the driver through thesecond impedance matching unit and reamplifies the power.

In an implementation, the applied voltage control circuit adjustsvoltage applied to the power stage in order for the power stage to beoff in the first power mode and in order for the power stage to be on inthe second power mode.

In an implementation, the impedance transformer is connected in aparallel branch to the second impedance matching unit, the power stageand the third impedance matching unit, and in the first power mode, theimpedance transformer receives through the first impedance matching unitthe power amplified by the driver and outputs the power to the fourthimpedance matching unit. Further, in a specific implementation, theimpedance transformer has the structure of a band-pass filter. In itsother implementation, the impedance transformer may be any type ofband-selective filter including band-pass, band reject, low pass, orhigh pass.

In an implementation, the third impedance matching unit prevents powertransferred through the impedance transformer from leaking to the powerstage.

In an implementation, the fourth impedance matching unit receives powerfrom the impedance transformer in the first power mode and the fourthimpedance matching unit receives power from the third impedance matchingunit in the second power mode.

In an implementation, a path, that power which passed through the firstimpedance matching unit is transferred to the fourth impedance matchingunit, is determined by comparing impedance as viewed from the firstimpedance matching unit towards the power stage and impedance as viewedfrom the first impedance matching unit towards the impedancetransformer.

In an implementation, the impedance as viewed from the first impedancematching unit towards the impedance transformer forms a part of aninterstage matching unit between the driver and the power stage togetherwith the first impedance matching unit in the second power mode.

In another embodiment, a multiple power mode power amplifier with highefficiency includes a driver for variably amplifying gain of inputsignal using a variable gain amplifier; a power stage for receivingpower amplified by the driver through a first impedance matching unitconnected to the driver in serial and a second impedance matching unitconnected to the first impedance matching unit, reamplifying the powerand outputting the reamplified power; an applied voltage control unit,connected to the power stage, for controlling an applied voltagecorresponding to the first power mode and the second power mode; animpedance transformer for receiving through the first impedance matchingunit power amplified by the driver according to operations of theapplied voltage control circuit; a third impedance matching unit,connected to the power stage in serial, for receiving power amplified bythe power stage according to operations of the applied power controlcircuit; and a fourth impedance matching unit, connected to the thirdimpedance matching unit and connected to the impedance transformer, fortransferring the power transferred from the third impedance matchingunit or the impedance transformer, to an output stage according tooperations of the applied voltage control circuit.

In an implementation, the power stage is connected to the secondimpedance matching unit in serial, and in the second power mode, thepower stage receives through the second impedance matching unit poweramplified by the driver and reamplifies the power.

In an implementation, the applied voltage control circuit controls thedriver in order for gain of signal inputted into the driver to bedifferently amplified corresponding to the first power mode and thesecond power mode. The applied voltage control circuit adjusts voltageapplied to the power stage in order for the power stage to be off in thefirst power mode and in order for the power stage to be on in the secondpower mode.

The amplifiers may have more than two power modes. For example, theamplifier may have three, four, five, six, or even greater number ofmodes, such as several different power modes using various amounts ofpower.

In an implementation, the impedance transformer is connected in parallelto a circuit branch including the second impedance matching unit, thepower stage, and the third impedance matching unit, and in the firstpower mode, the impedance transformer receives through the firstimpedance matching unit power amplified by the driver and outputs thepower to the fourth impedance matching unit. The impedance transformerhas the structure of a band-pass filter. In its other implementation,the impedance transformer may be any type of band-selective filterincluding band-pass, band reject, low pass, or high pass.

In an implementation, the third impedance matching unit prevents powertransferred through the impedance transformer from leaking to the powerstage.

In an implementation, the fourth impedance matching unit receives powerfrom the impedance transformer in the first power mode and the fourthimpedance matching unit receives power from the third impedance matchingunit in the second power mode.

In an implementation, a path, for power passing through the firstimpedance matching unit to the fourth impedance matching unit isdetermined by comparing an impedance as viewed from the first impedancematching unit towards the power stage and impedance as viewed from thefirst impedance matching unit towards the impedance transformer.

In an implementation, the impedance as viewed from the first impedancematching unit towards the impedance transformer forms a part of aninterstage matching unit between the driver and the power stage togetherwith the first impedance matching unit in the second power mode.

In one embodiment, a multiple power mode amplifier configured for use ina portable electronic device includes a driver to provide power. A powerstage transistor includes an input node and an output node. The inputnode of the power stage transistor is coupled to the driver to receivethe power from the driver in a high power mode. An impedance transformerincludes an input node and an output node and is provided in a parallelbranch to the power stage transistor. The input node of the impedancetransformer is configured to receive the power from the driver in a lowpower mode.

In another embodiment, a portable electronic device includes a powersource and a power amplifier coupled to the power source. The poweramplifier includes a driver to provide power; a power stage transistorincluding an input node and an output node, the input node of the powerstage transistor being coupled to the driver to receive the power fromthe driver and configured to receive power from the driver in a highpower mode; and an impedance transformer including an input node and anoutput node and provided in a parallel branch to the power stagetransistor, the input node of the impedance transformer being configuredto receive the power from the driver in a low power mode.

In another embodiment, a multiple power mode amplifier configured foruse in a mobile phone includes a driver to provide power; a power stagetransistor including an input node and an output node, the input node ofthe power stage transistor being coupled to the driver and beingconfigured to receive the power from the driver during a high power modeoperation; a first impedance matching unit coupled to the driver toreceive the power output by the driver; a second impedance matching unitprovided between the first impedance matching unit and the power stagetransistor; an impedance transformer including an input node and anoutput node and provided in a parallel branch to the power stagetransistor, the input node of the impedance transformer being configuredto receive the power from the first impedance matching unit during a lowpower mode operation; a third impedance matching unit having a firstside and a second side, the first side of the third impedance matchingunit being coupled to the output node of the power stage transistor; anda fourth impedance matching unit being coupled to the second side of thethird impedance matching unit and the output node of the impedancetransformer.

In yet another embodiment, a multiple power mode power amplifierincludes a power stage transistor configured to receive first power froma driver via first and second impedance matching units during a highpower mode and output second power that is greater than the first power;an applied voltage control circuit coupled to the power stage transistorand configured to apply a first signal to the power stage transistorduring the high power mode to turn on the power stage transistor andapply a second signal to the power stage transistor during a low powermode to turn off the power stage transistor; an impedance transformerconfigured to receive third power from the driver via the firstimpedance matching unit during the low power mode, the third power beingless than the second power; a third impedance matching unit coupled tothe power stage transistor in series and configured to receive thesecond power output by the power stage transistor during the high powermode; and a fourth impedance matching unit coupled to the thirdimpedance matching unit in series and configured to receive the secondpower from the third impedance matching unit or third power from theimpedance transformer and transfer the received second or third power toan output stage.

According to another aspect, the invention includes the use of anamplifier circuit having multiple modes and without switches in awireless transmitter or transceiver device such as a mobile telephone.The invention includes the use of an amplifier circuit having multiplemodes and without switches to extend transmit time of a portablewireless device. The invention includes the use of an amplifier circuithaving multiple modes and without switches to increase the battery lifeof a portable wireless device. The invention includes the use of anamplifier circuit having two or more modes without switches to operatein a low power or a high power mode depending on a distance to areceiving antenna, thus improving efficiency and reducing powerconsumption. The invention includes the use of a change in an impedanceof a power stage to change from a low power mode to a high power mode,or vice versa, without using switches. The invention includes the use ofimpedance network to change from one power mode to another power modefor an amplifier without switches.

Another aspect of the invention is to provide a bias modulation circuitto change the biasing to an amplifier to reduce its power consumption.This is different from the technique of switching an amplifier so it isoff. By changing the biasing of an amplifier, its mode of operation maybe changed so it operates in class AB mode closer to class B than classA. With this technique, power consumption in the low power mode isfurther reduced for an amplifier module over an amplifier module withoutthe bias modulation circuit.

Other objects, features, and advantages of the present invention willbecome apparent upon consideration of the following detailed descriptionand the accompanying drawings, in which like reference designationsrepresent like features throughout the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a conventional multiple power mode power amplifierusing bypass switches.

FIG. 2 illustrates a conventional multiple power mode power amplifierusing other bypass switches.

FIG. 3A illustrates a conventional multiple power mode power amplifierusing a bypass switch, of which the switch is connected to an outputterminal of λ/4 bypass transmission line.

FIG. 3B illustrates a conventional multiple power mode power amplifierusing a bypass switch, of which the switch is connected to an inputterminal of λ/4 bypass transmission line.

FIG. 4 illustrates a conventional multiple power mode power amplifierusing other bypass switches.

FIG. 5 illustrates a multiple power mode power amplifier with highefficiency using power mode transition structure without a bypass switchaccording to one embodiment of the present invention.

FIG. 6 illustrates the multiple power mode power amplifier with highefficiency illustrated in FIG. 5 in detail for explaining power modetransition structure without a bypass switch.

FIG. 7A is a graph illustrating gain characteristic corresponding to thehigh power mode and the low power mode of the multiple power mode poweramplifier according to one embodiment of the present invention.

FIG. 7B is a graph illustrating power added efficiency (PAE)characteristic corresponding to the high power mode and the low powermode of the multiple power mode power amplifier according to oneembodiment of the present invention.

FIG. 8 shows a more detailed circuit diagram of a two-stageimplementation of the multiple power mode amplifier.

FIG. 9 shows an alternative embodiment of a multiple power modeamplifier where driver 110 is a variable gain amplifier (VGA) orpredistorter circuit.

FIG. 10 shows another alternative embodiment of a multiple power modeamplifier having three stages, two drivers and one power stage.

FIG. 11 shows an alternative embodiment of a three-stage multiple powermode amplifier where one of the drivers is a variable gain amplifier orpredistorter circuit.

FIG. 12 shows another alternative embodiment of a three-stage multiplepower mode amplifier, but the bypass path with impedance transformationnetwork bypasses only the main power stage.

FIG. 13 shows a more detailed circuit diagram of the amplifier circuitin FIG. 12.

FIG. 14 shows an alternative embodiment of the amplifier circuit in FIG.12 where one of the drivers is a variable gain amplifier orpredistorter.

FIG. 15 shows various different circuit arrangements for impedancematching network 1 and impedance matching network 2.

FIG. 16 shows various different circuit arrangements for impedancematching network 3 and impedance matching network 4.

FIG. 17 shows various different circuit arrangements for the impedancetransformation network.

FIG. 18 shows a more detailed circuit diagram of an implementation ofthe amplifier circuit of FIG. 14.

FIG. 19 shows various different circuit arrangements for the voltagecontrol circuitry.

FIG. 20 shows a two-stage multiple mode amplifier circuit of theinvention implemented using CMOS technology.

FIG. 21 shows a three-stage multiple mode amplifier circuit of theinvention implemented using CMOS technology.

FIG. 22 shows a two-stage multiple mode amplifier circuit of theinvention implemented using MESFET technology.

FIG. 23 shows a three-stage multiple mode amplifier circuit of theinvention implemented using MESFET technology.

FIG. 24 shows an implementation of the amplifier circuit of FIG. 5 withbias modulation circuitry.

FIG. 25 shows an embodiment of the three-stage amplifier configurationof FIG. 12 with amplifier bias modulation.

FIGS. 26A and 26B further illustrate the reduced bias supply concept ofthe invention.

FIG. 27 shows more detailed circuit diagram of the scheme of FIG. 26Brespectively.

FIG. 28 shows four examples of the driver stage control circuitry.

FIG. 29A shows a voltage control circuit connected to an amplifierdriver for altering its bias voltage.

FIGS. 29B and 29C show graphs of how R1 or R2 can be used to fine tunethe bias supply current to the driver 2 transistor at the design stage.

FIG. 30 shows a graph of the current variation versus the output power.

FIG. 31 shows a graph of the efficiency (PAE) versus the output power.

FIG. 32 shows a graph of the ACPR versus the output power.

FIG. 33 shows a graph of the gain versus the output power.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a conventional multiple power mode power amplifierusing bypass switches or bypass switch circuits. The multiple power modepower amplifier illustrated in FIG. 1 is configured using three bypassswitch circuits.

If the power amplifier is operated in the high power mode, both a firstswitch 31 and a second switch 32 are closed and a third switch 33 isopen, so that output of a driver 10 including an impedance matching unitis input into a power stage 22 (or power amplifying component). Incontrast, if the power amplifier is operated in the low power mode, boththe first switch 31 and the second switch 32 are open and the thirdswitch 33 is closed, so that output of the driver 10 including theimpedance matching unit bypasses the power stage 22.

The multiple power mode amplifier illustrated in FIG. 1 hasdisadvantages in that the size of the entire system increases and powerloss of the entire system increases due to power loss of the bypassswitch circuits. Especially, power loss of the second switch 32connected to an output terminal of the power stage affects greatly theefficiency and linearity of the operation in the high power mode, sothat a bypass switch circuit having great power capacity and excellentloss characteristic should be used; however, the use of a bypassswitching circuit with a large power handling capability and extremelylow power loss requires high cost.

For example, a typical switch may be a PIN diode that has a −1 dB gain.When there are multiple switches in series (i.e., serial switches), thegain loss is cumulative. Also PIN diodes are typically not integratedwith the amplifier, which increases the number of integrated circuits(ICs) or chips or components needed. This increases cost. Also, PINdiodes themselves are relatively costly to include in a circuit. Someexamples of other types of switches are relays, micromachined switches,transistor switches, PIN diode switches, and Schottky diode switches.

A switch can be made out of active or passive devices. Some commonactive device switches are PIN diodes, Schottky diodes, and transistors.The term “active” means that DC supply and power consumption are neededfor the device to operate properly.

A switch may also be implemented using passive devices such asmechanical relays. Also, recently with the development of MEMS(microelectromechanical system) technology, the micromachined mechanicalswitches are also possible, which can be used in the integratedcircuits. For passive switches, no power consumption is needed, butcontrol DC signals are still needed for operation.

All in all, these can all be categorized as switches or switch devices,and they share three distinct features. They add loss to the signals andadd cost to the whole system. Also, external control signals are neededto turn on and off the switches.

FIG. 2 illustrates a conventional multiple power mode power amplifierusing other bypass switch circuits. The multiple power mode poweramplifier illustrated in FIG. 2 is configured using a combination of aSPDT (single-pole and double-throw) switch and a shunt (not serial)switch in the bypass path.

An input signal to be amplified is coupled to a pole 41 of a switch 44.The switch 44 can be operated so as to couple the input signal at pole41 to either throw 42 or to throw 43. The throw 43 is coupled to theinput of a power amplifying stage 45. The output of the power amplifyingstage 45 is coupled to a first side of a first impedance-transformingunit 47. A second side of the unit 47 is coupled to an output node 50.The throw 42 is coupled to a first side of a secondimpedance-transforming unit 46. A third impedance transforming unit 48has a first side directly coupled to the second side of impedancetransforming network 47 and to the output node 50. A second side of theimpedance transforming unit 48 is switched by a switch 49 between asecond side of impedance transforming unit 46 and ground.

The operation of switch 49 is coordinated with the operation of switch44. The impedance transforming units have impedance values selected sothat in a high power mode, i.e., when the input signal is coupled viathe switch 44 to the amplifying stage 45, the output of the amplifyingstage 45 sees the correct load impedance through the impedancetransforming unit 47. When operating in a low power mode, i.e., whenswitch 44 connects to the throw 42 and routes the input signal via theimpedance transforming unit 46, the input signal also sees the correctload impedance through the impedance transforming unit 46.

Since the power amplifier illustrated in FIG. 2 should use at least twosingle pole double-throw (SPDT) switches, characteristic gets worse dueto inherent losses of the switches and manufacturing costs alsoincreases due to use of relatively expensive switches and a bigger poweramplifying stage.

FIG. 3 a illustrates a conventional multiple power mode power amplifierusing a bypass switch circuit, of which switching circuit is connectedto an output terminal of λ/4 bypass transmission line. The multiplepower mode power amplifier illustrated in FIG. 3 a includes a carrieramplifier 51 and has a bypass implemented by a bypass switch circuitconfigured by using λ/4 bypass transmission line 52 and a shunt switch53.

In a high power mode, the shunt switch 53 of the bypass switch circuitis connected to the ground and the bypass switching circuit includingthe shunt switch 53 is operated as a short-circuited stub by beingconnected to the λ/4 bypass transmission line 52, and presents an opencircuit seen from the carrier amplifier.

In a low power mode, the shunt switch 53 of the bypass switching circuitis connected to an output terminal of the carrier amplifier 51 and isoperated as a bypass together with the λ/4 bypass transmission line 52.

FIG. 3 b illustrates a conventional multiple power mode power amplifierusing a bypass switch circuit, of which the switch circuit is connectedto an input terminal of λ/4 bypass transmission line.

A difference between the multiple power mode power amplifier illustratedin FIG. 3 b and the multiple power mode power amplifier illustrated inFIG. 3 a is only the order of a λ/4 bypass transmission line and abypass switch circuit.

Since the multiple power mode power amplifier illustrated in FIGS. 3 aand 3 b includes only one bypass switch circuit, it has an advantage inthat the size of the entire system is small. However, at the same time,it has a disadvantage in that bandwidth is limited due to use of a λ/4bypass transmission line and requires a large area to accommodate thelong transmission line.

FIG. 4 illustrates a conventional multiple power mode power amplifierusing other bypass switch circuits. The power amplifier includes aninput stage transistor 62, an output amplifier stage transistor 65, aserial switch 66 comprising two parallel diodes, and a switchingtransistor 68.

In a high power mode, the switching transistor 68 is off and the serialswitch 66 is open. Accordingly, output of the input stage transistor 62is inputted into the output stage transistor 65 and a first impedancematching unit 63 that transforms input impedance into impedance of 15ohms.

In a low power mode, base bias of the output stage transistor 65 is offand the switching transistor 68 is on, so that the switch 66 is closed.A second impedance matching unit 64 transforms load impedance intoimpedance of 25 ohms. The second impedance matching unit 64 has smallerimpedance than input impedance of the output stage transistor 65 whenthe switch 66 is closed and has bigger impedance than input impedance ofthe output stage transistor 65 when the switch 66 is open. Thus, thesecond impedance matching unit 64 operates as a bypass.

In the following part of this patent, a detailed explanation is givenwith reference to the attached drawings as to the multiple power modepower amplifier with high efficiency in accordance with embodiments ofthe present invention. As used in the application, a first power mode isalso referred to as the low power mode, and a second power mode is alsoreferred as the high power mode.

FIG. 5 illustrates a multiple power mode power amplifier with highefficiency using power mode transition structure without a bypass switchcircuit according to one embodiment of the present invention. In otherwords, the amplifier does not include any switches or switch devices inits circuitry. As has been mentioned above, some examples of switchesinclude relays, micromachined switches, transistor switches, PIN diodeswitches, and Schottky diode switches.

The approach of the present invention does not use any switches and isfree from external control circuits provided to control the switches andthe added cost and loss due to having switches. This allows one toimplement a circuit such as a multiple mode amplifier in a compact,simple manner and a cost-effective way. Further, no loss means that theperformance (i.e., linearity and efficiency) can be maximized. Althoughdescribed respect to a multiple mode amplifier, techniques of thepresent invention may be applied to other types of circuit besidesamplifiers.

The multiple power mode power amplifier with high efficiency illustratedin FIG. 5 includes: a driver 100 for amplifying input power; a powerstage 120 for receiving power amplified by the driver 100 through afirst impedance matching unit 130 connected to the driver and a secondimpedance matching unit 140 connected to the first impedance matchingunit 130, reamplifying the power and outputting the reamplified power;an applied voltage control circuit 90, connected to the power stage 120,for controlling applied voltages corresponding to the low power mode andthe high power mode; an impedance transformer 170 for receiving poweramplified by the driver 100 through the first impedance matching unit130, according to operations of the applied voltage control circuit 90and transferring the power to a fourth impedance matching unit 160; athird impedance matching unit 150, connected to the power stage 120 inserial, for transferring power amplified by the power stage 120 to thefourth impedance matching unit 160; and the fourth impedance matchingunit 160, connected to the third impedance matching unit 150 andconnected to the impedance transformer 170, for transferring power,transferred from the third impedance matching unit 150 or the impedancetransformer 170, to an output stage 78 according to operations of theapplied voltage control circuit 90.

As will be explained below, in one embodiment, the power stage 120includes one or more transistors to regulate the flow of power throughit. The power stage 120 may also amplify the power received from thedriver 100 during high power mode operation. Accordingly, the powerstage 120 may also refer to a “power amplifier stage” or “power stagetransistor.” In an embodiment, the power stage includes one or moretransistors. Further details are provided below. A transistor to amplifya signal in the signal path may be called a power stage transistor. Thistransistor may include one or more transistors connected in parallel.

The applied voltage control circuit 90 adjusts a voltage applied to thepower stage 120 by exterior control signal inputs corresponding to thelow power mode and the high power mode. Since output power is reduced inthe low power mode by passing through not the power stage 120, but theoptimized first impedance matching unit 130 and the optimized impedancetransformer 170, the applied voltage control circuit 90 adjusts thevoltage applied to the power stage 120 in order for transistors of thepower stage 120 to be off. This reduces power consumption.

In contrast, in the high power mode, since output power is increased bypassing through the first impedance matching unit 130, the secondimpedance matching unit 140 and the power stage 120, the applied voltagecontrol circuit 90 applies voltage appropriate for operations oftransistors of the power stage 120. This increases power consumption.

In the low power mode, the driver 100 amplifies input power andtransfers the amplified power to the impedance transformer 170 throughthe optimized first impedance matching unit 130. In contrast, in thehigh power mode, the driver 100 amplifies input power and transfers theamplified power to the power stage 120 through the optimized firstimpedance matching unit 130 and the optimized second impedance matchingunit 140.

The power stage 120 in the low power mode is turned off by the appliedvoltage control circuit 90, while in the high power mode, the powerstage 120 is turned on and amplifies the signal to be transmitted,amplified by the driver 100 and inputted into the power stage 120.

The first impedance matching unit 130 is a circuit optimized for optimaloperations corresponding to the low power mode and the high power mode.The first impedance matching unit 130 transfers input power amplified bythe driver 100 corresponding to the operation mode to the impedancetransformer 170 or the power stage 120.

The second impedance matching unit 140 is a circuit optimized foroptimal operations corresponding to the low power mode and the highpower mode. In the low power mode, the second impedance matching unit140 routes power, amplified by the driver 100 and transferred throughthe first impedance matching unit 130, to the impedance transformer 170and in the high power mode, to the power stage 120. In the high powermode, the second impedance matching circuit acts also as an interstagematching circuit, allowing high efficiency power transfer from thedriver to the power stage. The second impedance matching unit works inconjunction with the first impedance unit and impedance transformer forthis purpose to provide power matching.

The impedance transformer 170 is an impedance transforming circuit thattransforms impedance appropriately corresponding to the low power modeor the high power mode. In the low power mode, the impedance transformer170 forms a path that bypasses the power stage 120, so that output ofthe driver 100 is transferred through node 76 to output 78 of the poweramplifier.

FIG. 6 illustrates the multiple power mode power amplifier with highefficiency illustrated in FIG. 5 in more detail for explaining the powermode transition structure without bypass switching circuit.

Output power of the driver 100 reaches a junction 72. At junction 72,the path divides corresponding to power modes via the first impedancematching unit 130.

In the low power mode, the power stage 120 is off by voltage applied bythe applied voltage control circuit 90, and input impedance Z_(INT-H) ofthe power stage 120 as viewed from the first impedance matching unit 130(see FIG. 5) is larger than input impedance Z_(INT-L) of a pathbypassing the power stage 120 as viewed from the first impedancematching unit 130. The input impedance Z_(INT-H) may be significantly orsubstantially larger than the input impedance Z_(INT-L). In animplementation, Z_(INT-H) is about two times larger than Z_(INT-L). Inan implementation, Z_(INT-H) is about three times larger than Z_(INT-L).In an implementation, Z_(INT-H) is more than two times larger thanZ_(INT-L). In an implementation, Z_(INT-H) is more than three timeslarger than Z_(INT-L). In an implementation, Z_(INT-H) is in a rangefrom about two to about three times larger than Z_(INT-L). In animplementation, Z_(INT-H) is less than about three times larger thanZ_(INT-L). In an implementation, Z_(INT-H) is greater than two largerthan Z_(INT-L), but less than about three times larger than Z_(INT-L).

The design of impedance transformer 170 is optimized in conjunction withthe third impedance matching unit 150 and the fourth impedance matchingunit 160 to lower the impedance level as viewed from the first impedancematching unit 130 in the low power mode. Thus, a power signal amplifiedby the driver 100 and transferred to the junction 72 is optimized sothat the amount of power inputted into the impedance transformer 170 issignificantly or substantially larger than the amount of power inputtedinto the power stage 120. The output power signal is transferred to theoutput stage 78 with minimizing power leakage to the power stage byimpedance transforming action of 170 in conjunction with the thirdimpedance matching unit 150 and the fourth impedance matching unit 160.

In the high power mode, the power stage 120 is on, controlled by avoltage applied by the applied voltage control circuit 90, and inputimpedance Z_(INT-H) of the power stage 120 as viewed from the firstimpedance matching unit 130 is smaller than input impedance Z_(INT-L) ofa path bypassing the power stage 120 as viewed from the first impedancematching unit 130. The impedance transformer 170 is optimally designedin conjunction with the third impedance matching unit 150 and the fourthimpedance matching unit 160 to increase Z_(INT-L) of a bypass path wellabove Z_(INT-H) of the power stage 120 in the high power mode. Thesecond impedance matching unit 140 is designed to boost up the impedancelevel as viewed from the first impedance matching unit 130 whileproviding interstage matching in the high power mode. Thus, most power,amplified by the driver 100 and transferred to the junction 72, isamplified by the power stage 120 and is transferred to the output stage78 of the power amplifier, while minimizing power leakage to theimpedance transformer 170 by the optimized third impedance matching unit150 and the optimized fourth impedance matching unit 160.

Input impedance Z_(INT-L) of a path bypassing the power stage 120 asviewed from the first impedance matching unit 130 forms an interstagematching unit between the driver 100 and the power stage 120 togetherwith the first impedance matching unit 130 and the second impedancematching unit 140 in the high power mode, so that output power of thedriver 100 is well transferred to the power stage 120 without powerreflections.

In the high power mode, the input impedance Z_(INT-L) may besignificantly or substantially larger than the input impedanceZ_(INT-H). In an implementation, Z_(INT-L) is about two times largerthan Z_(INT-H). In an implementation, Z_(INT-L) is about three timeslarger than Z_(INT-H). In an implementation, Z_(INT-L) is more than twotimes larger than Z_(INT-H). In an implementation, Z_(INT-L) is morethan three times larger than Z_(INT-H). In an implementation, Z_(INT-L)is in a range from about two to about three times larger than Z_(INT-H).In an implementation, Z_(INT-L) is less than about three times largerthan Z_(INT-H). In an implementation, Z_(INT-L) is at least two timeslarger than Z_(INT-H), but less than about three times larger thanZ_(INT-H).

In the low power mode, the power stage is in what may be referred to asan off state, and in the high power mode, the power stage is in what maybe referred to as an on state. In the on state, the power stage consumessignificantly more power than in the off state. Furthermore, in animplementation, an input impedance to the power stage is about two timeslarger in the off state as compared to the on state. In animplementation, an input impedance to the power stage is greater thanabout two times larger in the off state as compared to the on state.

FIG. 7 a is a graph illustrating a gain characteristic corresponding tothe high power mode and the low power mode of the multiple power modepower amplifier according to one embodiment of the present invention.

In the low power mode, the power stage 120 is off, controlled by theapplied voltage control circuit 90, so that an output of the driver 100is not amplified by the power stage 120 and the output of the driver 100is transferred to the output stage 78 through the impedance transformer170. Thus, the gain characteristic is different from that when theoutput of the driver 100 is amplified by the power stage 120. The dottedline shows the gain when the power stage is on, while the solid lineshows the gain when the power stage is off. In the low power mode, DCpower is not consumed by the power stage 120, so that power addedefficiency (PAE) characteristic is excellent. PAE is ((Pout−Pin)/Pdc).In FIG. 7 b, the PAE when the power stage is on is shown by the dottedline, and when the power stage is off, the PAE is the solid line. Usingthe techniques of the invention, the amplifier has an excellent PAE inlow power mode.

In contrast, in the high power mode, an output of the driver 100 isamplified by the power stage 120 and reaches the output stage 78 so thata power gain is added to the output of the driver 100 and the PAEcharacteristic depends on the power stage 120 that has generally highoutput power level.

Accordingly, as illustrated in FIG. 7 a, a gain characteristic iscomparatively low (i.e., gain of A) in the low power mode and gaincharacteristic is comparatively high (i.e., gain of B) in the high powermode.

FIG. 7 b is a graph illustrating a power added efficiency (PAE)characteristic corresponding to the high power mode and the low powermode of the multiple power mode power amplifier according to oneembodiment of the present invention.

As illustrated in FIG. 7 b, a PAE characteristic in the low power mode(see solid line) is excellent because DC power consumption by the powerstage 120 can be removed. In the high power mode, output of the powerstage 120 is transferred to the output stage 78 through the thirdimpedance matching unit 150 and the fourth impedance matching unit 160,and the third impedance matching unit 150, the fourth impedance matchingunit 160 and the impedance transformer 170 do not use a switch, so thatoutput of the power stage 120 is transferred to the output stage 78without loss and thus PAE characteristic in the high power mode isexcellent.

FIG. 8 shows a more detailed circuit diagram of a specificimplementation of the multiple power mode amplifier of FIG. 5. Aspecific circuit implementation for the first impedance matching circuit130 of FIG. 5 is shown within the box 130 of FIG. 8. A specific circuitimplementation for the second impedance matching circuit 140 of FIG. 5is shown within the box 140 of FIG. 8. A specific circuit implementationfor the third impedance matching circuit 150 of FIG. 5 is shown withinthe box 150 of FIG. 8. A specific circuit implementation for the fourthimpedance matching circuit 160 of FIG. 5 is shown within the box 160 ofFIG. 8. A specific circuit implementation for the impedance transformercircuit 170 of FIG. 5 is shown within the box 170 of FIG. 8. A specificcircuit implementation for the driver circuit 100 of FIG. 5 is shownwithin the box 100 of FIG. 8. A specific circuit implementation for thepower stage circuit 120 of FIG. 5 is shown within the box 120 of FIG. 8.A specific circuit implementation for the applied voltage controlcircuit 90 of FIG. 5 is shown within the box 90 of FIG. 8.

FIG. 8 also shows an input matching circuit 80, not shown in FIG. 5,which is used to provide impedance at the input to prevent or minimizereflected waves. This is merely an example of an input matching circuitand there are many other circuit configurations that may be used.

An input signal is connected to the power mode amplifier at node 70 tothe input matching circuit 80. Within input matching circuit 80, aninductor 9003 is connected between 70 and a node 9006, a capacitor 9009is coupled between node 9011, and a capacitor 9013 is connected betweennode 9006 and a reference voltage line, ground.

The implementation of FIG. 8 uses bipolar junction transistors (BJTs).However, in other embodiments, the invention may use heterostructurebipolar transistors, heterojunction bipolar transistors, MOStransistors, field effect transistors (FETs), MESFETs, JFETs, BiCMOS,triodes, complementary metal-oxide semiconductor (CMOS) transistortechnology, metal-oxide semiconductor transistors, p-type metal-oxidesemiconductor transistors, n-type metal-oxide semiconductor transistors,high electron mobility transistors, or metal semiconductor field effecttransistors, and their analogous devices, and other types of activedevices, in any combination. These devices may be fabricated usingsemiconductor technology including silicon, gallium arsenide, siliconover insulator, or silicon germanium. One or more devices may also befabricated using nanotechnology. Furthermore, the particular type of BJTshown is an npn-type device. However, it is understood that with thenecessary changes, the circuitry may also use pnp-type device types. Asa further example, NMOS (or n-channel MOSFET) or PMOS (or p-channelMOSFET) devices may be used. CMOS process technology allows themanufacture of NMOS and PMOS device types for a single integratedcircuit.

Driver 100 includes a BJT transistor Q5, which may be referred to as adriver transistor, having its base connected to 9011 and its emittercoupled to the reference voltage (ground in a specific embodiment). Acollector of Q5 is connected to node 9015, which is an output of thedriver and input to first impedance matching unit 130. The circuitryshown for the driver is merely an example of a driver circuit that maybe used, and other amplifier designs may be used. Driver 100 is acommon-emitter-type amplifier circuit. Other types of amplifier circuitconfigurations that may be used include common base, cascade, andcascode. These amplifier circuits may require different bias circuitsand voltages or currents that shown or described in FIG. 8, andappropriate changes to the circuitry may be made.

DC power is provided to Q5 via two voltage sources, a voltage1 and avoltage2. Voltage2 is provided to node 9011 through a transistor 9017and resistance or impedance 9019. A capacitor or capacitance 9021 isconnected between voltage2 and the reference voltage. A base electrodeof transistor 9017 is connected to a node 9023. A resistor 9025 isconnected between voltage1 and node 9023. Two diodes are connectedbetween node 9023 and the reference voltage. Although two diodes areshown, any number of diodes (for a voltage drop) may be used to providea bias voltage. More diodes will generally provide a greater voltagedrop.

In a specific embodiment, voltage1 is about 2.85 volts. Voltage1 may bea relatively constant voltage provided to the multiple power modeamplifier circuit from a source such as a voltage regulator. Asdiscussed previously, one particular application of the circuitry is forbattery-operated devices such as a mobile or cellular phone where powerwill be supplied by a battery. In such an application, the specificlevels of one or more voltage sources may vary depending on batteryconditions. When freshly charged, a battery typically provides a highervoltage level output and depending on the specific battery technology orchemistry (e.g., nickel metal hydride, nickel cadmium, lithium ion, andlead acid), this voltage level gradually drops as the battery isdrained. In a specific embodiment, voltage2 is a voltage source having alevel depending on the battery state. For example, when the battery isfully charged, voltage2 may be 4.2 volts, and when the battery is almostempty or completely drained, voltage2 may be about 3.2 volts. Theamplifier circuitry in FIG. 8 should operate properly under all voltageconditions of the battery. Typically, the worst case operatingconditions are given when at the lowest voltage level seen during normaloperation, which occurs when the battery is almost empty.

First impedance matching unit 130 is connected between node 9015 andnode 72. In the implementation in FIG. 8, the first impedance matchingunit includes a transmission line 9028 connected between node 9015 andvoltage2, a capacitor 9030 connected between voltage2 and the referencevoltage, and a capacitor 9032 connected between node 9015 and node 72.

The transmission line may simply be a line or wire that can be modeledas a ladder network of series inductors and shunt capacitors.Characteristics of the transmission line depend on length and width ofthe line or wire, and these are design parameters. In an embodiment, atransmission line is a line having an electrical line length 1/10 orgreater of a guided wavelength within a medium. The wavelength typicallychanges depending on the specific medium. For example, a wavelength willbe different if the medium is air versus a semiconductor. For asemiconductor medium and a 2 gigahertz signal, a transmission line mayhave a line length of about 10 microns or more. A width of this line maybe about 5 microns or more.

In another embodiment, a transmission line is a line having anelectrical line length 1/20 or greater of a guided wavelength in amedium. In another embodiment, a transmission line is a line having anelectrical line length 1/30 or greater of a guided wavelength in amedium. In another embodiment, a transmission line is a line having anelectrical line length 1/50 or greater of a guided wavelength in amedium. In another embodiment, a transmission line is a line having anelectrical line length 1/50 or greater of a guided wavelength in amedium. In another embodiment, a transmission line is a line having anelectrical line length 1/100 or greater of a guided wavelength in amedium.

Second impedance matching unit 140 is connected between node 72 and anode 74. In the implementation in FIG. 8, the second impedance matchingunit includes an inductor 9037 connected between node 72 and thereference voltage, and a capacitor 9039 connected between node 72 and74. An inductor in this circuit or any of the circuits of the inventionmay be implemented using any technique to provide an inductance device.Some examples of inductance devices or implementations of inductorsinclude wire bonding, transmission line, microstrip line, strip line,coaxial cable, or coplanar waveguide. Any of these or combinations ofthese may be used to implement inductances in the invention, such asthose indicated by the inductor symbol in the circuit diagrams.

Impedance transformer circuit 170 is connected between node 72 and anode 76. In the implementation in FIG. 8, the impedance transformercircuit includes a capacitor 9042 connected between node 72 and a node9042, a capacitor 9046 connected between node 9044 and the referencevoltage, and an inductor 9048 is connected between node 9044 and node76.

Power stage 120 is connected between node 74 and node 9116. Power stageis an amplifier circuit including a BJT transistor Q6 having its baseconnected to node 74, a collector connected to node 9116, and an emitterconnected to the reference voltage. Power stage 120, like driver 100, isa common-emitter-type amplifier circuit. Other types of amplifiercircuit configurations that may be used include common base, cascade,and cascode. These amplifier circuits may require different biascircuits and voltages or currents that shown or described in FIG. 8, andappropriate changes to the circuitry may be made. Also, power stage 120may be a different type of amplifier circuit from driver 100.

The power stage may be turned on or off depending on a voltage at thevoltage control node 9051. FIG. 8 shows a specific implementation of theapplied voltage control circuit 90. Other circuits may be used thatperform a similar function. The amplifier circuit will be in a low powermode when the voltage control node is at a first level (e.g., about alevel of voltage1 or 2.85 volts). The circuit will be in a high powermode when the voltage control node is at a second level (e.g., about alevel of the reference voltage or ground or 0 volts). When in the lowpower mode, transistor Q6 will be in a high impedance mode and drawlittle current. When in the high power mode, transistor Q6 will beoperating and draw current to amplify its input signal. In anembodiment, in the high power mode, the power stage will provide fromabout 5 to 15 decibels (dB) of gain. However, the exact is dependent onthe transistor or device technology used and also on how the amplifiercircuit is biased. Examples of other embodiments of the multiple modeamplifier implemented using other technologies such as CMOS and MESFETare discussed below.

In operation, depending on the voltage level at node 9051, current fromvoltage1 goes through node 9103 and will pass either (a) through atransistor 9105 to the reference voltage line or (b) through atransistor 9108 to node 74, the base of transistor Q6. When in the lowpower mode, node 9051 will be 2.85 volts, relatively little currentpasses through transistor 9108, compared to the path through transistor9105, and the base of Q6 will be at about the reference voltage or 0volts so the power stage will be essentially off. When in the high powermode, node 9051 will be at the reference voltage or 0 volts, relativelylittle current passes through transistor 9105, compared to the paththrough transistor 9108, and the base of Q6 will be at about 1.0 voltand 1.4 volts so the power stage will be operating or on.

Third impedance matching unit 150 is connected between node 9116 and 76.In the implementation in FIG. 8, the third impedance matching unitincludes a transmission line 9072 connected between node 76 and voltage2and a capacitor 9074 connected between voltage2 and the reference level.In a specific implementation, capacitor 9074 is relatively large such asabout 100 picofarads. This capacitor provides an RF or virtual ground atvoltage2 and also stabilizes voltage 2. A capacitor 9119 is between node9116 and the reference level. An inductor 9122 is connected betweennodes 9116 and 76.

Inductor 9122 may be formed on the same integrated circuit as one ormore other components in the MMIC box of FIG. 8. In a specificembodiment, inductor 9122 is formed using a wire bond line between node9116 and components at node 76. Furthermore, inductor 9122 may be formedusing a passive component such as an inductor coil.

In an embodiment, components shown within the MMIC box are on-chip,which means they are included on a single integrated circuit such as thesame semiconductor die or semiconductor body. By including as manycomponents as possible on a single integrated circuit, this reducescosts and reduces the amount of space required by the amplifier. This isespecially important for portable electronics where consumers desiremore compact form factors. In other embodiments, one or more of thecomponents shown within in the MMIC box may be off-chip by usingdiscrete components or on different integrated circuits. For example, asdiscussed above, inductor 9122 may be off-chip. In another embodiment,input matching circuit 80 is off-chip.

Fourth impedance matching unit 160 is connected between node 76 and anoutput signal node 240. In the implementation in FIG. 8, the fourthimpedance matching unit includes a transmission line 9082 connectedbetween node 76 and a node 9084, a capacitor 9086 connected between node76 and the reference level, a capacitor 9088 connected between node 9084and the reference level, and a capacitor 9090 connected between node9084 and output signal 240. In an embodiment, capacitor 9086 is anoptional capacitor and may be omitted in some embodiments of theinvention. Furthermore, in some embodiments, this capacitor may beimplemented using parasitic capacitance. Some examples of parasiticcapacitance include capacitance of a line or other conductor (e.g., longline length), capacitance of a transistor gate, and capacitance at anode due to a number of devices or size of devices or componentsattached to that node.

FIG. 9 shows an alternative embodiment of the invention where driver 110is a variable gain amplifier (VGA). A gain control circuit 91 generatesa signal to control a gain of the driver. The circuitry in FIG. 9operates similarly and provides the same benefits of the circuitry inFIG. 5. However, the implementation in FIG. 9 has the additional featurewhere the gain can be varied by using driver 110.

This circuit configuration may be used when a particular applicationrequires variable gain. This circuit may also be used in a fixed-gainapplication, in which case a gain of driver 110 is fixed. This allowsthe same circuitry to be used in multiple applications, without the needto having different parts. Furthermore, wireless telephone standardsvary and different gains may be required for different systems, so thevariable gain version of the invention can be used to address thedifferent system specifications, without requiring a separate part foreach standard. For example, an amplifier of the invention may beprogrammed electrically, by fuses, laser cutting, programmable cells, orother techniques after fabrication.

Alternatively, in a fixed-gain application, driver 110 may work as apredistorter circuit. A predistorter circuit provides overemphasis tocompensate for gain roll off of the main stage amplifier. Generally aspower goes up, gain of an amplifier rolls off. To compensate for thisgain roll off in main stage 120, driver or predistorter circuit 110increases its gain as power goes up, so the total gain of the circuitry(amplifiers 110 and 120) will be more constant, increasing the linearityof the amplifier, especially in the high power region. Therefore, whenusing a predistorter 110, the circuitry will provide a fixed gain for awider power range.

FIG. 9 provides a basic two-amplifier implementation of the invention.The first stage can be either fixed gain or variable gain amplifierstage. In the latter case, it can be used as a predistorter. The basicconcept is to bypass one or more stages in the multiple stage amplifiersto reduce the DC current consumption. For example, for N-stageamplifiers, Nth, (N−1)th, and so forth second stages can be bypassedusing bypass switching circuits without any switches. It is preferableto bypass later stages (Nth for example) since they consume more DCcurrent. Voltage control circuitry 90 turns off the main stage when inthe low power mode. Impedance transformation network 170 works as abypass circuit. The core idea is that this circuit does not include anycostly switches but still functions as a bypass switching circuit, whichis made possible by optimizing impedance matching networks 1, 2, 3, and4.

In a specific implementation, the invention is an integrated circuithaving a first circuit branch, connected between a first node and asecond node, where the first circuit branch has N amplifier stages inseries, where N is an integer 0 or greater. There is a second circuitbranch, connected between the second node and a third node, where thesecond circuit branch has M amplifier stages in series, where M is aninteger 1 or greater. There is a third circuit branch, connected betweenthe second node and the third node, where the third circuit branch hasan impedance transformer unit. During a first mode of operation of thecircuit, at least one amplifier stage of the M amplifier stages of thesecond branch is in an off state, consuming less power than in an onstate, and a signal output from the N amplifier stages of the firstbranch passes substantially through the third circuit branch. During asecond mode of operation of the circuit, the M amplifier stages of thesecond circuit branch are in the on state and a signal output from Namplifier stages of the first branch passes substantially through thesecond circuit branch. In operation, when N is 0 and M is 1 or greater,the bypassing circuit may bypass all the amplifier stages of theamplifier, meaning there is either amplification or no amplification.

FIG. 10 shows another alternative embodiment of the invention having twodrivers and one power stage. Compared to the FIG. 5 implementation, thisamplifier circuit further includes a driver2 105, controlled by thevoltage control circuit 90, and an impedance matching network 5 145,which are in between the impedance matching network 2 circuit 140 andmain power stage 120. Driver1 100 may have a fixed gain or may have avariable gain (or may be a predistorter), such as driver 110 in FIG. 9.Note that for this configuration at a bypass node, node 72, there is animpedance matching network for each branch (i.e., impedance matchingnetwork 1 130, impedance matching network 2 140, and impedancetransformation network 170).

FIG. 11 shows a configuration where driver1 110 is a variable gainamplifier, controlled by gain control circuitry 91. Besides thisdifference, the circuitry operates similarly as that in FIG. 10. Duringthe operation of this three-stage amplifier configuration, both third(last and main) and second stages may be bypassed so that only the firststage is turned on all the time. In this case, voltage control circuitryturns off the second and third stages when in the low power mode.

The FIG. 10 circuit has a maximum of three gain stages, while thecircuit in FIG. 5 has a maximum of two gain stages. The bypass path withimpedance transformation network 170 bypasses both driver2 and the mainpower stage. When in the low power mode, both driver2 and main powerstage will be off and draw minimal current. When in the high power mode,both driver2 and main power stage will be on and provide gain.

Because there are more gain stages, typically the circuit in FIG. 10 hasmore gain than the circuit in FIG. 5. Further, because there are moreindividual stages in FIG. 10, there are more degrees of freedom in thedesign, which makes its design and utilization more flexible. This maymake designing a multiple mode amplifier with certain technologies suchgallium arsenide versus silicon. Gallium arsenide technology amplifierstypically provide greater gain, so typically fewer amplification stagesare needed to obtain the same gain as with a technology such as silicon.

FIG. 12 shows another embodiment of an amplifier circuit. Thisembodiment is similar to FIG. 10 there are three amplifiers stages toboost the gain. But the bypass path with impedance transformationnetwork bypasses only the main power stage, not the driver2 stage as inFIG. 10.

This circuit provides less power savings than the one in FIG. 10 becauseonly the main power stage will be bypassed instead of both driver 2 andmain power stages.

FIG. 13 shows a more detailed circuit diagram of the amplifier circuitin FIG. 12. Details of each of the block of FIG. 12 are shown in boxesindicated by similar reference numbers. The details are similar asdiscussed above for FIG. 8, except for blocks 85 and 105. In thisembodiment, the amplifier circuit in driver2 105 is similar to theamplifier circuit in main driver 120 but the sizes of the transistorsmay be smaller. However, as discussed above, other amplifier circuitdesigns and configurations may be used, and in any combination for themultiple mode amplifier.

FIG. 14 shows a similar amplifier circuit as FIG. 12, but driver 110 isa variable gain amplifier or predistorter to provide the benefits asdiscussed above. FIG. 14 is based on the similar to the concept asdescribed in FIG. 9, but the concept has been extended to three stagesin FIG. 14.

FIG. 15 shows various different circuit arrangements for impedancematching network 1 block 130 and impedance matching network 2 block 140.Any of these circuits may be substituted in corresponding block in themultiple mode amplifier circuits previously described including FIGS. 5and 8 to 14.

For example, for configuration 15-1, block 130 of the multiple modeamplifier circuit may be replaced by what is shown within box 1605, andblock 140 may be replaced by what is shown within box 1607. Thiscombination of circuitry in 1605 and 1607 would provide the impedancematching networks 1 and 2 functionality, as discussed above. Othercombinations of circuits are shown in configurations 15-2 to 15-8. Anyof these alternative embodiments of circuits may be used to form amultimode amplifier circuit of the present invention. FIG. 15 showsexamples of the possible circuit combinations and is not meant to beexhaustive. Other combinations are possible.

FIG. 16 shows various different circuit arrangements for impedancematching network 3 block 150 and impedance matching network 4 block 160.Any of these circuits may be substituted in corresponding block in theamplifier circuits in FIGS. 5, and 8 to 14.

For example, for configuration 16-1, block 150 of the multiple modeamplifier circuit may be replaced by what is shown within box 1705, andblock 160 may be replaced by what is shown within box 1707. Thiscombination of circuitry in 1705 and 1707 would provide the impedancematching networks 3 and 4 functionality, as discussed above. Othercombinations of circuits are shown in configurations 16-2 to 16-9. Anyof these alternative embodiments of circuits may be used to form amultimode amplifier circuit of the present invention. FIG. 16 merelyshows examples of the possible circuit combinations and is not meant tobe exhaustive. Other combinations are possible.

FIG. 17 shows various different circuit arrangements for impedancetransformation network block 170. Any of these circuits may besubstituted in corresponding block in the amplifier circuits in FIGS. 5,and 8 to 14.

For example, for configuration 17-1, block 170 of the multiple modeamplifier circuit may be replaced by what is shown within box 1805. Thecircuitry in 1805 would provide the impedance transformation networkfunctionality, as discussed above. Other circuits are shown inconfigurations 17-2 to 17-8. Any of these alternative embodiments ofcircuits may be used to form a multimode amplifier circuit of thepresent invention. FIG. 17 merely shows examples of the possiblecircuits and is not meant to be exhaustive. Other circuits are possible.

FIG. 18 shows a more detailed circuit diagram of FIG. 14. However, inthe circuitry of FIG. 18, first impedance matching circuit 130 isomitted. Therefore, the impedance transformation network 170 isconnected directly to driver stage amplifier Q5 at node 72. Also,impedance transformation network 170 is realized using a singleinductor. The net effect is thus a reduction in component count,resulting in a reduced cost of the amplifier module.

For implementing a amplifier according to the invention, as the FIG. 18example shows, there is no need to use all the impedance matchingnetworks, 130, 140, 150, and 160, to realize the concepts of theinvention. By optimizing the other impedance matching networks 140, 150,160, and impedance transformation network 170, one or more of theimpedance matching networks can be eliminated. For example, in animplementation, impedance matching network 2 140 may be omitted. Inanother implementation, impedance matching network 3 150 may be omitted.In another implementation, impedance matching network 4 160 may beomitted. And in further embodiments, any combination of these impedancematching networks may be omitted.

FIG. 19 shows various different circuit arrangements for the voltagecontrol circuitry 90. Any of these circuits may be substituted incorresponding block in the amplifier circuits in FIGS. 5, and 8 to 14.

For example, for configuration 19-1, block 90 of the multiple modeamplifier circuit may be replaced by what is shown within box 1905. Thecircuitry in 1905 would provide the voltage control circuitryfunctionality, as discussed above. Other circuits are shown inconfigurations 19-2 to 19-4. Any of these alternative embodiments ofcircuits may be used to form a multimode amplifier circuit of thepresent invention. FIG. 19 merely shows examples of the possiblecircuits and is not meant to be exhaustive. Other circuits are possible.

FIG. 20 shows a multiple mode amplifier circuit of the inventionimplemented using CMOS technology. This is a two-stage implementationsuch as shown in FIG. 5. This figure shows merely an example of anembodiment of the invention, and other embodiments are possible. Forexample, any of the alternative circuit configurations for the circuitryshown in FIGS. 15 to 17 and 19 may be substituted for the blocks in FIG.20.

FIG. 21 shows a multiple mode amplifier circuit of the inventionimplemented using CMOS technology. This is a three-stage implementationsuch as shown in FIG. 12. This figure shows merely an example of anembodiment of the invention, and other embodiments are possible. Forexample, any of the alternative circuit configurations for the circuitryshown in FIGS. 15 to 17 and 19 may be substituted for the blocks in FIG.21.

FIG. 22 shows a multiple mode amplifier circuit of the inventionimplemented using MESFET technology. This is a two-stage implementationsuch as shown in FIG. 5. This figure shows merely an example of anembodiment of the invention, and other embodiments are possible. Forexample, any of the alternative circuit configurations for the circuitryshown in FIGS. 15 to 17 and 19 may be substituted for the blocks in FIG.22.

FIG. 23 shows a multiple mode amplifier circuit of the inventionimplemented using MESFET technology. This is a three-stageimplementation such as shown in FIG. 12. This figure shows merely anexample of an embodiment of the invention, and other embodiments arepossible. For example, any of the alternative circuit configurations forthe circuitry shown in FIGS. 15 to 17 and 19 may be substituted for theblocks in FIG. 23.

FIG. 24 shows an implementation of the amplifier circuit of FIG. 5 withbias modulation circuitry. FIG. 24 additionally shows a voltage controlcircuitry2 95 for a bias modulation circuit. The bias modulation circuitof this implementation is shown as a single block, but in otherimplementations, the circuitry may be divided among two or more blocks.A mode control voltage (not shown) is connected to voltage controlcircuitry2 95 to control operation of the circuitry. The voltage controlcircuitry2 95 is connected to driver 100 and power stage 120. Inoperation, the mode control voltage controls the operation of voltagecontrol circuitry2 95. Depending on the mode control voltage, thevoltage control circuitry2 95 will change biasing of driver 100 in orderto alter it operating characteristics and place the power stage 120 inan on state or an off state.

In an embodiment, the mode control voltage and the voltage controlcircuitry2 95 is used to change the biasing of driver 100 to lower thepower consumption of the driver 100 used to implement the amplifier. Anamplifier has various modes of operations or design such as class A,class AB, class B, and other classes. Full class A operation of anamplifier refers to a very linear transfer curve, but high powerconsumption because the output transistors draw current all the time,until the amplifier starts to clip. Therefore, class A amplifier havelow distortion but high power consumption, and consequently generate alot of heat. A class B amplifier has zero standby current and startsconsuming power when there is a signal. Although a class B amplifier hasgood power efficiency, this type of amplifier typically has significantdistortion, especially when compared to a type A amplifier.

An amplifier may operate somewhere between class A and class B and willbe known as a class AB amplifier. A class AB amplifier has current flowfor more than half, but less than all, of the input cycle. In theinvention, in the low power mode, the biasing of an amplifier, such asdriver 100, may be changed so that the amplifier will save additionalpower, but at the same time, provide a good output characteristic.Depending on the number of amplifiers in the circuitry, this techniqueof the invention may used to provide varying degrees of powerconsumption and gain or amplification.

For example, for the circuitry in FIG. 24, in the high power mode, thepower stage 120 is on and the driver 100 is on. In the low power mode,the power stage 120 is off and driver 100 is on. This is similar to theamplifier circuit in FIG. 5. However, in FIG. 24, the voltage controlcircuitry2 95 may additionally change (e.g., reduce) the biasing ofdriver 100 to lower its power consumption, compared to that in FIG. 5.In other words, although driver 100 is on in both high and low powermodes, driver 100 will have lower power consumption in the low powermode than it will have when in the high power mode. This providesadditional power savings. This aspect of the invention may be applied toany amplifier of the circuitry to provide additional power savings.

The bias modulation circuitry of the invention may be added to all thepower amplifier module configurations described in this patent, two- ,three-, four-, and N-stage implementations. FIG. 24 is provided as asimple example to explain the concepts of the invention, but similarcircuitry and techniques may be applied to the other power amplifiermodule configurations. For example, bias modulation circuitry may beused in the power amplifier modules configuration in FIGS. 5, 8, 9, 10,11, 12, 13, 14, 18, 20, 21, 22, and 23.

This voltage control circuitry2 95 for bias modulation takes the modecontrol signal, and when in the low power mode, it reduces the biascurrent to the first-stage transistor. A difference between the voltagecontrol circuitry 90 and this voltage control circuitry2 95 for biasmodulation is the fact that bias control modulation circuitry does notturn off the bias, but just reduces the bias supply in the low powermode. In this way, the bias supply to the first-stage transistor isreduced in the low power mode, maximizing the efficiency in the lowpower mode. The addition of this circuit allows further enhancedefficiencies in the low power mode.

FIG. 25 shows an embodiment of the three-stage amplifier configurationof FIG. 12 with amplifier bias modulation. In FIG. 12, the switchlessswitching power amplifier turns off one or more of the stages when inthe low power mode. For example, in the three-stage implementation ofFIG. 12, voltage control circuitry 90 turns off the last stage (powerstage 120) when in the lower power mode. In the FIG. 25 configuration,additional bias modulation circuitry is included in driver 2 105 so thatreduced bias supply current (quiescent current) to driver 2 can beapplied in the low-power mode. In other words, in the lower power mode,the main transistor is turned off, and additionally, driver 2 transistoris biased at the reduced bias current level (such as class AB, butcloser to class B). In this way, there is will be a further improvementin the low-power mode efficiency.

FIGS. 26A and 26B further illustrate the reduced bias supply concept ofthe invention. In FIG. 26A, the control signal (Vcntr) effectively turnson or off the main stage control circuit, reducing the overall powerconsumption when the main stage is off. In the scheme of FIG. 26B, themode control signal (Vcntr) turns off the main stage transistor using amain stage bias control circuit 90. At the same time, it also reducesthe bias current to the driver transistor using a driver stage controlcircuit 96. As noted above, the circuitry in block 95 may be dividedinto multiple blocks. For example, the main stage control circuit may bein a different block from driver stage control circuit 96.

FIG. 27 shows a more detailed circuit diagram of a specificimplementation of a bias modulation circuit scheme of FIG. 26B. FIG. 27shows the details of control circuitry in box 95. Box 95 has circuitry90 as in FIG. 26A. Further, in box 95 is the bias modulation circuitrydiscussed above, which reduces the bias voltage to the driver 2transistor, reducing its power consumption in the low power modefurther. There are two voltage levels, Vref and VCC, also labeled asconstant voltage1 and constant voltage2, respectively. In operation,depending the mode control voltage (Vcntr), the main transistor driverwill be on or off, and the driver2 transistor will be specific mode ofoperation, say a high bias or low bias mode, where the high bias modeprovide more amplification at the cost of higher power than in the lowbias mode. In operation, when increasing a voltage Vcntr, a bias voltageat the driver2 will decrease. When decreasing a voltage Vcntr, a biasvoltage at the driver2 will increase. Therefore, the bias voltage atdriver2 has a negative relationship with respect to Vcntr. However, inother implementations, the relationship between Vcntr and driver2 may bepositive, where an increase at Vcntr increases the bias voltage, and adecrease at Vcntr decreases the bias voltage. Furthermore, the circuitryin FIG. 27 shows a common Vcntr signal used for both the box 90 and box96 circuitry. In other implementations, these may be separate signals.

FIG. 28 shows four examples of the driver stage control circuitry.Configuration 28-1 has two resistors or impedances (besides an impedanceconnected to Vcntr) for fine tuning the driver2 bias. However, only oneresistor or impedance (besides an impedance connected to Vcntr) may beneeded such as configuration 28-2 and 28-3. Another alternative is touse a combination of a resistor or impedance and one or more levelshifting diodes such as in configuration 28-4. Generally, a greaternumber of diodes means there is a greater voltage or potentialdifference. Any of these configurations may be substituted for circuitry96 in FIG. 27.

FIG. 29A shows a voltage control circuit connected to an amplifierdriver for altering its bias voltage. FIGS. 29B and 29C show graphs ofhow R1 or R2 can be used to fine tune the bias supply current to driver2transistor at the design stage. By using smaller R1 and R2 resistorsduring the design, the quiescent current of the driver2 stage transistoris reduced. The extreme case of this curves will be when R1 and R2 are0, in which case, the driver2 stage is almost turned off as in the caseof main-stage transistor in the low power mode (see the bias controlcircuit 90 of the main-stage transistor).

FIG. 30 shows a graph of the current variation versus the output power.The bias modulation concept allows further reduction in the overall biascurrent in the low power mode by reducing the driver2 bias current aswell. It is worthwhile to note that the current reduction is morepredominant in the real low-power region, which is advantageous in aspecific application of improving the talk time a CDMA-based handset. Inthe graph, the solid line is for the power amplifier module (PAM) withbias modulation to reduce power consumption. The dotted line is for thepower amplifier module with only switching (i.e., to turn the mainamplifier off).

FIG. 31 shows a graph of the efficiency (PAE) versus the output power.Reduced current consumption translates into further improvedefficiencies in the low power mode. In the graph, the solid line is forthe power amplifier module with bias modulation to reduce powerconsumption. The dotted line is for the power amplifier module with onlyswitching (i.e., to turn the main amplifier off).

FIG. 32 shows a graph of the ACPR versus the output power. By furtherreducing the bias current in the low power mode, compromised linearityis naturally expected. However, these results are still within theallowable limit. In other words, in this concept, we try to minimize theoverall current consumption by compromising the linearity more whilestill staying within the limit of system (e.g., a CDMA system).

FIG. 33 shows a graph of the gain versus the output power. By furtherreducing the bias current in the low power mode, the bias to the driver2 stage is almost close to class-B case rather than class-AB. It isnatural and customary to see the gain expansion as the output power isincreased in the class-B amplifiers. This graph clearly shows such again variation in the low power mode. The gain step can be about 2 dBwhen the overall quiescent current is reduced to 10 milliamps. The basicpower amplifier configuration of the invention (without biasmodulations) gives an overall quiescent current of 22 milliamps.

The embodiments of the present invention have been described above forpurposes of illustrating the present invention. It is not intended to beexhaustive or to limit the invention to the precise form described. Manymodifications and variations are possible in light of the teachingabove. Accordingly, the scope of the invention is defined by theappended claims.

1. An integrated circuit comprising: a first circuit branch, coupledbetween a first node and a second node, comprising N amplifier stages inseries, wherein N is an integer 0 or greater, a second circuit branch,coupled between the second node and a third node, comprising M amplifierstages in series, wherein M is an integer 1 or greater; a voltagecontrol circuit coupled to the least one amplifier stage of the Mamplifier stages of the second branch, wherein the voltage controlcircuit, in response to a mode control voltage, provides a controlsignal to the least one amplifier stage of the M amplifier stages of thesecond branch to place the at least one amplifier stage of the Mamplifier stages of the second branch in an on state or an off state;and a third circuit branch, coupled between the second node and thethird node, comprising an impedance transformer unit, wherein during afirst mode of operation of the circuit, at least one amplifier stage ofthe M amplifier stages of the second branch is in an off state,consuming less power than in an on state, and a signal output from the Namplifier stages of the first branch passes substantially through thethird circuit branch, and during a second mode of operation of thecircuit, the M amplifier stages of the second circuit branch are in theon state and a signal output from N amplifier stages of the first branchpasses substantially through the second circuit branch.
 2. An integratedcircuit comprising: a first circuit branch, coupled between a first nodeand a second node, comprising N amplifier stages in series, wherein N isan integer 0 or greater, a second circuit branch, coupled between thesecond node and a third node, comprising M amplifier stages in series,wherein M is an integer 1 or greater; and a third circuit branch,coupled between the second node and the third node, comprising animpedance transformer unit, wherein during a first mode of operation ofthe circuit, at least one amplifier stage of the M amplifier stages ofthe second branch is in an off state, consuming less power than in an onstate, and a signal output from the N amplifier stages of the firstbranch passes substantially through the third circuit branch, and duringa second mode of operation of the circuit, the M amplifier stages of thesecond circuit branch are in the on state and a signal output from Namplifier stages of the first branch passes substantially through thesecond circuit branch; and wherein a gain of at least one amplifierstage of the N amplifier stages of the first branch is variable.
 3. Theintegrated circuit of claim 1 wherein a gain of at least one amplifierstage of the N amplifier stages of the first branch is fixed.
 4. Theintegrated circuit of claim 2 wherein at least one amplifier stage ofthe N amplifier stages of the first branch comprises a predistortercircuit.
 5. The integrated circuit of claim 2 wherein at least oneamplifier stage of the N amplifier stages of the first branch comprisesa gain characteristic to compensate for nonlinearities in a gaincharacteristic of at least one amplifier stage of M amplifier stages ofthe second branch.
 6. The integrated circuit of claim 2 wherein a gaincharacteristic of the circuit, after passing through both the firstbranch and the second branch, is more linear than the gaincharacteristic of the second branch.
 7. The integrated circuit of claim1 wherein the first circuit branch, second circuit branch, and thirdcircuit branch are formed on a single semiconductor substrate.
 8. Theintegrated circuit of claim 2 further comprising a voltage controlcircuit coupled to the least one amplifier stage of the M amplifierstages of the second branch, wherein the voltage control circuit, inresponse to a mode control voltage, provides a control signal to theleast one amplifier stage of the M amplifier stages of the second branchto place the least one amplifier stage of the M amplifier stages of thesecond branch in an on state or an off state.
 9. The integrated circuitof claim 2 further comprising: a voltage control circuit coupled to atleast one amplifier stage of the N amplifier stages of the first branchand the at least one amplifier stage of the M amplifier stages of thesecond branch, wherein the voltage control circuit, in response to amode control voltage, provides a first signal to the at least oneamplifier stage of the N amplifier stages of the first branch to adjusta bias of the at least one amplifier stage of the N amplifier stages ofthe first branch so during the first mode of operation the bias of theat least one amplifier stage of the N amplifier stages of the firstbranch is reduced compared to the bias of the at least one amplifierstage of the N amplifier stages of the first branch during the secondmode of operation, and the voltage control circuit, in response to themode control voltage, provides a second signal to the at least oneamplifier stage of the M amplifier stages of the second branch to placethe at least one amplifier stage of the M amplifier stages of the secondbranch in the on state or the off state.
 10. The integrated circuit ofclaim 2 further comprising: a voltage control circuit coupled to atleast one amplifier stage of the N amplifier stages of the first branchand the at least one amplifier stage of the M amplifier stages of thesecond branch, wherein the voltage control circuit, in response to amode control voltage, provides a first signal to the at least oneamplifier stage of the N amplifier stages of the first branch to adjusta bias current of the at least one amplifier stage of the N amplifierstages of the first branch so during the first mode of operation thebias current of the at least one amplifier stage of the N amplifierstages of the first branch is reduced compared to the bias current ofthe at least one amplifier stage of the N amplifier stages of the firstbranch during the second mode of operation, and the voltage controlcircuit, in response to the mode control voltage, provides a secondsignal to the at least one amplifier stage of the M amplifier stages ofthe second branch to place the at least one amplifier stage of the Mamplifier stages of the second branch in the on state or the off state.11. The integrated circuit of claim 8 wherein the voltage controlcircuit comprises a transistor coupled between the least one amplifierstage of the M amplifier stages of the second branch and a referencevoltage level, wherein an electrode of the transistor is coupled to avoltage control line.
 12. The integrated circuit of claim 8 wherein thevoltage control circuit comprises a transistor coupled between the leastone amplifier stage of the M amplifier stages of the second branch and areference voltage level and another transistor coupled between a supplyvoltage line and a reference voltage level, wherein an electrode of theformer transistor is connected to the coupled point of the lattertransistor toward the supply voltage line and an electrode of the lattertransistor is coupled to a voltage control line.
 13. The integratedcircuit of claim 8 wherein the voltage control circuit comprises atransistor coupled between the least one amplifier stage of the Mamplifier stages of the second branch and a reference voltage level andanother transistor coupled between a supply voltage line and anelectrode of the former transistor, wherein an electrode of the formertransistor is coupled to the latter transistor and an electrode of thelatter transistor is coupled to a voltage control line.
 14. Anintegrated circuit comprising: a first circuit branch, coupled between afirst node and a second node, comprising N amplifier stages in series,wherein N is an integer 0 or greater, a voltage control circuit coupledto the least one amplifier stage of the N amplifier stages of the firstbranch, wherein the voltage control circuit, in response to the modecontrol voltage, provides a signal to the least one amplifier stage ofthe N amplifier stages of the first branch to adjust a bias of the leastone amplifier stage of the N amplifier stages of the first branch soduring the first mode of operation the bias of the least one amplifierstage of the N amplifier stages of the first branch is reduced comparedto the bias of the least one amplifier stage of the N amplifier stagesof the first branch during the second mode of operation; a secondcircuit branch, coupled between the second node and a third node,comprising M amplifier stages in series, wherein M is an integer 1 orgreater; and a third circuit branch, coupled between the second node andthe third node, comprising an impedance transformer unit, wherein duringa first mode of operation of the circuit, at least one amplifier stageof the M amplifier stages of the second branch is in an off state,consuming less power than in an on state, and a signal output from the Namplifier stages of the first branch passes substantially through thethird circuit branch, and during a second mode of operation of thecircuit, the M amplifier stages of the second circuit branch are in theon state and a signal output from N amplifier stages of the first branchpasses substantially through the second circuit branch.
 15. Theintegrated circuit of claim 14 wherein the voltage control circuitcomprises a transistor coupled to the least one amplifier stage of the Namplifier stages of the first branch through a resistance and coupled toa reference voltage level though a resistance, wherein an electrode ofthe third transistor is coupled to a voltage control line.
 16. Theintegrated circuit of claim 14 wherein the voltage control circuitcomprises a transistor coupled to the least one amplifier stage of the Namplifier stages of the first branch and coupled to a reference voltagelevel though a resistance, wherein an electrode of the transistor iscoupled to a voltage control line.
 17. The integrated circuit of claim14 wherein the voltage control circuit comprises a transistor coupled tothe least one amplifier stage of the N amplifier stages of the firstbranch through a resistance and coupled to a reference voltage level,wherein an electrode of the transistor is coupled to a voltage controlline.
 18. The integrated circuit of claim 14 wherein the voltage controlcircuit comprises: a transistor; a resistance; and one or more levelshifting diodes, connected in series with the resistance, wherein theresistance and the one or more level shifting diodes are coupled inseries to the least one amplifier stage of the N amplifier stages of thefirst branch, the transistor is coupled to the resistance and the one ormore level shifting diodes and coupled to a reference voltage level, andan electrode of the transistor is coupled to a voltage control line. 19.The integrated circuit of claim 2 wherein the integrated circuitcontains no bypass switches, wherein switches may include any of arelay, micromachined switch, transistor switch, PIN diode switch, orSchottky diode switch.
 20. The integrated circuit of claim 2 wherein thefirst branch, second branch and third branch contain no bypass switches,wherein switches may include any of a relay, micromachined switch,transistor switch, PIN diode switch, or Schottky diode switch.
 21. Theintegrated circuit of claim 1 wherein N is 0, 1, 2, 3, 4, or
 5. 22. Theintegrated circuit of claim 1 wherein M is 2, 3, 4, or
 5. 23. Theintegrated circuit of claim 1 wherein N is 0, 1, 2, 3, 4, or 5, and M is2, 3, 4, or 5.